Shutter devices are installed in ventilation devices for discharging air from a duct communicating with an outside (see Patent Document 1).
A conventional shutter device will be described with referring to FIGS. 6 and 7 below. FIG. 6 is a schematic view of the conventional shutter device. FIG. 7 is a front view of the shutter device.
As shown in FIGS. 6 and 7, the conventional shutter device includes an intake port 101 for having air entering therein, a discharging port 102 adapted to be connected with a side from which the air is discharged, a shutter 104 for blocking the air from an outside, and an adapter 105 including shutter support shafts 103 having the shutter 104 mounted thereto. The shutter device further includes a rib 106 operable to contact shutter 104 to seal a gap produced between the shutter 104 and an inner side of the discharging port 102 of the adapter 105 when the shutter 104 is closed. Rib 106 contacts an upper end of the shutter 104 at a side of the intake port 101, and contacts a lower end of the shutter 104 at a side approximating to the discharging port 102 with respect to the shutter support shafts 103. Rib 106 protrudes toward an inside of the discharging port 102, i.e., an air passage, at the side of the discharging port 102.
In the conventional shutter device, the rib 106 contacts the shutter 104 and seals the gap for improving air tightness when the shutter is closed. However, the rib 106 protrudes inward towards the air passage as seen from the front at the discharging port while the shutter opens. This arrangement increases the resistance in the air passage thus interrupting the flow of the air. For ensuring the desired flow of the air, the load to a fan and a motor increases for producing a large output. It is hence required to reduce the load to the fan and the motor while maintaining a desired level of the air-tightness.
Patent Document 1: JP2003-065581A